1. Field of the Invention
The present invention relates to the field of display techniques, and in particular to a reflective liquid crystal display (LCD) panel.
2. The Related Arts
The liquid crystal display (LCD) panel provides the advantages of thinness, low power consumption, without radiation, and is widely used in mobile phones, PDA, digital camera, PC screens or notebook PC screens.
Most LCD devices on the market are backlight-typed, which includes a backlight module, an LCD panel engaged to the backlight module, and a front frame fastening the LCD panel and the backlight module. The operation principle of the LCD panel is to place the liquid crystal (LC) molecules in two parallel glass substrates. A plurality of vertical and horizontal small wires is disposed between the two glass substrates. The LC molecules are controlled to change direction by powering on or off, and the light of the backlight module is refracted to produce an image.
At present, the LCD device is categorized, based on the type of light source, transmissive type LCD, reflective LCD, and transflective LCD.
With the rise of mobile devices and wearable applications, the demand for thinness and power saving of display devices is also growing. Therefore, the development of low power consumption display device becomes increasingly important. The traditional transmissive LCD has been massively produced, and the color, quality, resolution of the products are able to meet most of the needs. However, the LCD is relatively high power consumption when the display is used in mobile and wearable devices, which restricts usage time.
Because reflective LCD can display with ambient light without the need for energy-consuming backlights, the reflective LCD shows great potential in mobile devices and wearable display applications.
FIG. 1 shows a schematic view of a known reflective LCD panel. As shown in FIG. 1, the reflective LCD panel comprises: an upper substrate 100 and a lower substrate 200 disposed opposite to each other, and a liquid crystal layer 400 sandwiched between the upper substrate 100 and the lower substrates 200; the upper substrate 100 comprising: a first base substrate 110, a color filter (CF) layer 240 and a black matrix (BM) disposed on the first base substrate 110, a common electrode 120 disposed on the CF layer 240 and the BM 250; the lower substrate 200 comprising: a second base substrate 210, a thin film transistor (TFT) device layer 220 disposed on the second base substrate 210, and a pixel electrode 230 disposed on the TFT device layer 220; wherein the CF layer 240 comprising a transmissive red sub-pixel unit 310, a transmissive green sub-pixel unit 320 and a transmissive blue sub-pixel unit 330 separated by the BM 250; the pixel electrode 230 is a reflective electrode. The operation principle of the reflective LCD panel is that the ambient light passes through the CF layer 240 and the LC layer 400 to reach the pixel electrode 230. Then, the pixel electrode 230 reflects the light and the reflected light passes again through the LC layer 400 and the CF layer 240, and is emitted from the surface of the upper substrate 100 to realize image display. During the operation of the reflective LCD panel, ambient light passes back and forth through the CF layer 240 and the LC layer 400, resulting in relatively large loss of ambient light and low utilization, leading to insufficient brightness of the display screen of the LCD panel.
To improve the utilization of the ambient light by the reflective LCD panel, a reflective LCD panel as shown in FIG. 2 is proposed. As shown in FIG. 2, the reflective LCD panel comprises: an upper substrate 100 and a lower substrate 200 disposed opposite to each other, and a liquid crystal layer 400 sandwiched between the upper substrate 100 and the lower substrates 200; the upper substrate 100 comprising: a first base substrate 110 and a common electrode 120 disposed the first base substrate 110; the lower substrate 200 comprising: a second base substrate 210, a thin film transistor (TFT) device layer 220 disposed on the second base substrate 210, a pixel electrode 230 disposed on the TFT device layer 220, and a CF layer 240 and a BM 250 disposed on the pixel electrode 230; wherein the CF layer 240 comprising a reflective red sub-pixel unit 310′, a reflective green sub-pixel unit 320′ and a reflective blue sub-pixel unit 330′ separated by the BM 250; the pixel electrode 230 is a transparent electrode. Specifically, the reflective red sub-pixel unit 310′ can reflect red light and absorb green light and blue light, the reflective green sub-pixel unit 320′ can reflect green light and absorbs red light and blue light, and the blue reflective sub-pixel unit 330′ can reflect blue light and absorb red light and green light. The operation principle of the reflective LCD panel is that the ambient light passes through the LC layer 400 to reach the CF layer 240, and then the CF layer 240 selectively absorbs and reflects the light, and the reflected light passes through the LC layer 400 again and emits from the surface of the upper substrate 100 to realize image display. During the operation of the reflective LCD panel, the ambient light passes through the CF layer 240 only once, which reduces the loss of ambient light in the CF layer 240. However, since the CF layer 240 absorbs most of the spectrum and the ambient light needs to go through the structural layers such as the LC layer 400, the upper and lower alignment films (not shown) and the first base substrate 110 twice, the loss of ambient light is still large. Therefore, the brightness of the display screen of the LCD panel still needs improvement.